WEBVTT - From the Vault: Thirst, Part 2 0:00:05.880 --> 0:00:07.480 Hey, are you welcome to Stuff to Blow Your Mind? 0:00:07.520 --> 0:00:10.360 My name is Robert Lamb and I'm Joe McCormick, and 0:00:10.560 --> 0:00:13.399 we're running some vault episodes because we're out this week. 0:00:13.840 --> 0:00:17.639 This episode originally aired February third, twenty twenty two, and 0:00:17.640 --> 0:00:20.800 it's part two of our series on thirst. Get right 0:00:20.840 --> 0:00:26.279 in Welcome to Stuff to Blow Your Mind, a production 0:00:26.320 --> 0:00:35.760 of iHeartRadio. Hey, welcome to Stuff to Blow your Mind. 0:00:35.880 --> 0:00:38.479 My name is Robert Lamb and I'm Joe McCormick, and 0:00:38.520 --> 0:00:41.479 we're back with part two of our series on thirst. 0:00:41.920 --> 0:00:44.960 What are you drinking right now? Absolutely nothing? Oh no, wait, 0:00:45.000 --> 0:00:47.200 I do have I have water here at my desk. Water. 0:00:47.320 --> 0:00:50.360 I'm always drinking water. I'm a water guy. You know, 0:00:50.400 --> 0:00:53.440 some people are really into tea. I almost never drink tea. 0:00:53.600 --> 0:00:57.400 I go coffee water. That That's pretty much it during 0:00:57.400 --> 0:01:01.080 the daytime hours at least. Oh yeah, well, I'm currently 0:01:01.160 --> 0:01:07.960 drinking tea. I generally go coffee tea, tea, water tea, 0:01:08.319 --> 0:01:11.480 and then water, and then when the evening comes, you know, 0:01:11.600 --> 0:01:14.440 maybe I'll have something something else to drink. But yeah, 0:01:14.520 --> 0:01:18.720 right now it is tea, which is essentially water but 0:01:18.880 --> 0:01:21.200 with extra things added to it. You know, I sometimes 0:01:21.280 --> 0:01:25.080 get confused about what tea means because I think of 0:01:25.120 --> 0:01:28.680 tea as being a specific kind of plant, Like, isn't 0:01:28.720 --> 0:01:31.800 there a tea tree? Again, I don't know much about tea, 0:01:31.840 --> 0:01:35.160 so I think about it in that way. But then 0:01:35.319 --> 0:01:38.640 you can make a tea out of like anything basically 0:01:38.680 --> 0:01:41.360 that you steep in water, right, people make mushroom teas, 0:01:41.480 --> 0:01:43.160 people with all kinds of just like oh yeahs and 0:01:43.200 --> 0:01:46.840 plant stuff in water, and that's tea. Also, yeah, like 0:01:46.880 --> 0:01:48.760 I mean, there's there's proper tea, and that's generally what 0:01:48.840 --> 0:01:51.720 I'm what I'm drinking. I'm drinking, you know, a dark 0:01:51.720 --> 0:01:54.360 tea or maybe a green tea. But also sometimes I'll 0:01:54.400 --> 0:01:58.280 have a tumeric tea, which is like like tumeric and 0:01:58.360 --> 0:02:01.080 ginger and a little coconut oil and a little honey 0:02:01.320 --> 0:02:04.120 hot water. But it doesn't actually contain tea, So it's 0:02:04.520 --> 0:02:07.480 not completely accurate to call it such, because it's sort 0:02:07.480 --> 0:02:10.960 of how not all band aids are technically band aids 0:02:11.440 --> 0:02:14.640 or xeroxis or whatever. Has this been a terrible intro, 0:02:14.760 --> 0:02:17.000 Maybe we can cut my tea thing. No, No, this 0:02:17.040 --> 0:02:19.919 is a This is an intro that the people can 0:02:19.960 --> 0:02:22.040 relate to people are can have thoughts on this. It's 0:02:22.040 --> 0:02:24.639 always good to start off asking what a word means. 0:02:25.040 --> 0:02:27.520 So I turns out I know nothing about tea. I 0:02:27.520 --> 0:02:29.600 have no no, there you go. We need to come 0:02:29.600 --> 0:02:32.160 back and do an episode or a series of episodes 0:02:32.200 --> 0:02:36.160 on t It's a fascinating subject, fascinating history. Okay, well, 0:02:36.240 --> 0:02:39.080 we're going to jump back into some of the science 0:02:39.120 --> 0:02:41.200 that we were talking about in the last episode, where 0:02:41.240 --> 0:02:44.919 I was reviewing an interesting paper that I had read 0:02:44.960 --> 0:02:50.400 summarizing the recent state of research on the biology of thirst. 0:02:50.560 --> 0:02:53.400 That was it was a paper published in Current Biology. 0:02:53.960 --> 0:02:55.639 We had to break off in the middle of talking 0:02:55.639 --> 0:02:59.160 about it. But but before we get back into that, Rob, 0:02:59.200 --> 0:03:02.320 I think you want to talk about the taste of water, 0:03:02.400 --> 0:03:06.160 which I think is in itself a very interesting subject. Yeah, 0:03:06.160 --> 0:03:08.480 it's it's a strange one because we probably don't think 0:03:08.480 --> 0:03:11.720 about it enough, but but we often talk about it, 0:03:11.800 --> 0:03:14.280 especially when we when we travel from one place to another. 0:03:14.760 --> 0:03:18.120 UM we if you look back on I think back 0:03:18.400 --> 0:03:21.200 on water that you've consumed in the past, you may 0:03:21.240 --> 0:03:25.600 have specific memories of different waters. Um Like I remember 0:03:25.600 --> 0:03:28.520 when my family lived in the country and we had 0:03:28.560 --> 0:03:32.240 well water and it had it had a distinctive taste, 0:03:32.800 --> 0:03:35.240 and I don't I can't say that I loved it, 0:03:35.720 --> 0:03:38.360 But if I were to encounter the exact same flavor 0:03:38.400 --> 0:03:40.800 profile again, it would probably make me nostalgic, you know, 0:03:40.920 --> 0:03:44.320 like it it's it's a definite flavor that is tied 0:03:44.360 --> 0:03:46.720 to a definite place and time. Warning that this is 0:03:46.720 --> 0:03:48.640 a little crude, but I don't know of how else 0:03:48.680 --> 0:03:53.600 to explain it. You've ever been somewhere that had farty water, Um, well, 0:03:53.640 --> 0:03:56.200 it's kind of sulfury water. Yeah, it kind of kind 0:03:56.200 --> 0:03:58.840 of like water from the Yes, that's kind of what 0:03:58.880 --> 0:04:00.920 this was like. Yeah, it was that had kind of 0:04:00.960 --> 0:04:05.240 a fire and brimstone kind of flavor to it. Oh okay, 0:04:05.320 --> 0:04:06.960 that's a more elegant way to put it. Well, the 0:04:07.040 --> 0:04:09.360 denizens of Hell are not insalted. They're flatter that you 0:04:09.360 --> 0:04:12.720 would you would compare this foul drinking water two flats, 0:04:13.240 --> 0:04:17.080 uh huh. But um, you know, but then sometimes I 0:04:17.120 --> 0:04:19.160 don't know, there's there's also beech water, you know, like 0:04:19.200 --> 0:04:23.320 I anytime I'm in Florida and I'm having Florida water, 0:04:23.720 --> 0:04:25.480 like it has its own it tends to have its 0:04:25.480 --> 0:04:29.880 own bouquet, its own flavor. Profile that at the time 0:04:29.920 --> 0:04:32.640 I'm not enjoying, but then after I'm back and drinking 0:04:32.760 --> 0:04:35.880 taste your water, I'm kind of kind of long for it, 0:04:35.920 --> 0:04:39.080 you know, because like this is the water of the 0:04:39.200 --> 0:04:42.200 vacation that I am no longer on that sort of thing. 0:04:42.520 --> 0:04:44.719 I remember when I was in like a middle school, 0:04:44.760 --> 0:04:47.240 I went to New Mexico and we went somewhere there 0:04:47.240 --> 0:04:50.800 where the water was very I don't know, the tap 0:04:50.839 --> 0:04:54.200 water was almost kind of frothy somehow. It was like 0:04:54.240 --> 0:04:57.320 a kind of kind of white and cloudy, and I 0:04:57.320 --> 0:05:00.360 remember thinking it had a strange taste. I don't know 0:05:00.400 --> 0:05:02.200 what to connect that too, if it was supposed to 0:05:02.200 --> 0:05:05.720 be like that or not. Yeah, So I guess one 0:05:05.760 --> 0:05:10.080 thing we can definitely establish here is that there certainly 0:05:10.080 --> 0:05:12.960 seems to there is an objective difference in drinking waters 0:05:13.480 --> 0:05:17.520 from one place to another, Atlanta water versus Florida water, 0:05:17.560 --> 0:05:20.719 that sort of thing. But there's also this wide variety 0:05:20.839 --> 0:05:25.159 in how people just interpret the taste of water, you know. 0:05:25.200 --> 0:05:28.520 I think we often think of water as being neutral 0:05:28.720 --> 0:05:32.120 or tasteless. If you're mixing a cocktail, for example, you 0:05:32.120 --> 0:05:34.640 don't want to shake it too long with the crushed 0:05:34.640 --> 0:05:36.919 ice because you will what will happen, You will water 0:05:37.040 --> 0:05:40.160 it down. Water in this case is the antithesis of 0:05:40.160 --> 0:05:43.520 an interesting flavor profile. Well, but the other half of 0:05:43.560 --> 0:05:46.679 that is sometimes people screw up making a drink because 0:05:46.720 --> 0:05:48.400 they don't shake it with ice at all when they're 0:05:48.440 --> 0:05:51.880 supposed to, and they don't understand that shaking with ice 0:05:52.000 --> 0:05:54.400 not only cools the drink, but it also adds a 0:05:54.440 --> 0:05:56.560 certain amount of water to the drink, which is an 0:05:56.600 --> 0:06:00.480 important ingredient. Yes, absolutely so. You suppose to shake a 0:06:00.520 --> 0:06:02.400 cocktail and you don't, you end up with a drink 0:06:02.440 --> 0:06:05.599 that's usually too strong or too sweet. Yeah, there's a 0:06:05.600 --> 0:06:08.160 balance to be maintained there, much like the balance of 0:06:09.000 --> 0:06:11.120 water in the human body that we discussed in the 0:06:11.200 --> 0:06:13.480 last episode. Many of you out there have probably met 0:06:13.520 --> 0:06:15.880 someone who claims to not like the taste of water. 0:06:16.960 --> 0:06:21.560 Sometimes these individuals will will use flavored water or other 0:06:21.600 --> 0:06:23.840 beverages instead, and we'll tend to shy away from just 0:06:23.920 --> 0:06:27.920 drinking straight water. But I don't know if you're like me, 0:06:28.400 --> 0:06:31.080 you know, perhaps you've noticed times when a glass of 0:06:31.120 --> 0:06:34.560 ice water is just super satisfying. Um, you know, particularly 0:06:34.640 --> 0:06:37.279 on a hot day, like a just a super cold 0:06:37.320 --> 0:06:39.919 water lots of ice in it. Um I would, I 0:06:39.960 --> 0:06:43.720 would tend to. I found myself wanting to categorize that 0:06:43.800 --> 0:06:47.200 as delicious, though at the same time feeling weird for 0:06:47.279 --> 0:06:50.200 thinking that because it's like it's water. I can't say 0:06:50.200 --> 0:06:53.960 it's delicious. It has no flavor, right, that's what we believe. 0:06:54.560 --> 0:06:57.919 Another another one I really like is the first sip 0:06:57.960 --> 0:07:00.760 of cold water that I have after I have brushed 0:07:00.800 --> 0:07:04.159 my teeth. Now, after I've brushed my teeth and rinsed 0:07:04.160 --> 0:07:08.320 and spit I'm not drinking water that way, but yeah, like, 0:07:08.320 --> 0:07:10.640 after I've brushed my teeth, I've walked into another room, 0:07:10.800 --> 0:07:13.640 I have a sip of water, super cool and refreshing. Agreed, 0:07:13.760 --> 0:07:15.880 much better than the sip of orange juice after you've 0:07:15.880 --> 0:07:18.040 brushed your teeth, which is, Yeah, I don't know if 0:07:18.040 --> 0:07:23.120 you've ever tried that, it's famously disgusting. Oh this is 0:07:23.160 --> 0:07:26.040 this is always the worst. Really getting into the weeds here, 0:07:26.160 --> 0:07:30.440 but that that feeling when you you were you're busy 0:07:30.440 --> 0:07:32.880 in the morning, you go brush your teeth, you come 0:07:32.880 --> 0:07:34.960 back and you find your coffee cup and it still 0:07:35.000 --> 0:07:37.880 has half a cup of coffee in it. Oh, heartbreaking, 0:07:38.280 --> 0:07:40.080 because you know you can't drink it. Now. If you drink, 0:07:40.120 --> 0:07:42.040 you can drink it, you can you can throw it back, 0:07:42.240 --> 0:07:44.560 but it's going to taste awful. I wonder if anybody's 0:07:44.560 --> 0:07:46.880 ever done a controlled study of how long you have 0:07:47.040 --> 0:07:50.080 to wait after brushing your teeth before those those horrible 0:07:50.120 --> 0:07:53.840 flavor interactions fade away. I don't think it's too long, 0:07:54.000 --> 0:07:56.160 it's yeah. I mean, if I had to venture to guess, 0:07:56.160 --> 0:08:00.000 I'd say it couldn't be more than like twenty minutes, right, Yeah, 0:08:00.080 --> 0:08:01.040 of course, a lot of this, some of this is 0:08:01.040 --> 0:08:03.440 going to vary culture to culture. In some cultures, it's 0:08:03.480 --> 0:08:07.480 not it's not considered advisable to drink cold water. You 0:08:07.480 --> 0:08:10.920 want to drink hot water. So you know, there's it's 0:08:11.000 --> 0:08:12.520 gonna it's gonna it's gonna vary. There's a lot of 0:08:12.560 --> 0:08:15.040 cultural stuff going on here as well. Oh I've never 0:08:15.080 --> 0:08:17.360 heard of that. What's what's an example of a culture 0:08:17.400 --> 0:08:21.240 that favors hot water drinking. There's a connection if memory 0:08:21.240 --> 0:08:24.080 serves as a connection to traditional Chinese medicine here, where 0:08:25.400 --> 0:08:27.960 the idea is that it's better for your health to 0:08:28.120 --> 0:08:30.960 drink hot water as opposed to cold water. But I 0:08:30.960 --> 0:08:34.320 don't remember any of the deeper details of regarding it all. Right, Well, 0:08:34.320 --> 0:08:37.120 to get us back on track, you had mentioned that 0:08:38.520 --> 0:08:41.040 maybe maybe it was wrong to say that tap water, 0:08:41.280 --> 0:08:43.199 you know, cold water coming in on a hot day 0:08:43.320 --> 0:08:47.960 was delicious because water itself doesn't really have a taste. 0:08:48.000 --> 0:08:51.840 And I think this is a common understanding. But is 0:08:51.880 --> 0:08:54.880 that true? Like it does it have a taste? Does 0:08:54.920 --> 0:08:56.560 it not have a taste? Does it have a taste? 0:08:56.559 --> 0:09:00.720 We're just so used to that we can't taste it anymore. Yeah, 0:09:01.800 --> 0:09:04.880 we'll like to. Well, to go back to Aristotle, Aristotle 0:09:04.960 --> 0:09:08.000 was certainly kind of in the no taste camp, stating 0:09:08.040 --> 0:09:11.120 that it was for the most part tasteless. The idea 0:09:11.160 --> 0:09:14.440 that water is that it made liver flavors, but it's 0:09:15.160 --> 0:09:17.640 in and of itself does not have flavor. But a 0:09:17.679 --> 0:09:19.800 lot of a lot of work has gone into this 0:09:19.800 --> 0:09:24.240 this question. Uh, some some interesting studies. UM. I was 0:09:24.280 --> 0:09:28.520 reading an article by Berlin Game at All titled Understanding 0:09:28.520 --> 0:09:32.240 the Basics of Tapwater Taste, publishing the American Water Works 0:09:32.280 --> 0:09:36.800 Association Journal in two thousand and seven. UM, and they 0:09:36.840 --> 0:09:41.640 point out that the basically you get the water is 0:09:41.679 --> 0:09:45.960 going to contain negatively and positively charged ions as minerals, 0:09:46.480 --> 0:09:48.080 you're going to find that in your tap water, and 0:09:48.120 --> 0:09:52.560 that can positively and negatively affect taste. This is especially key, 0:09:52.600 --> 0:09:55.280 they point out as far as water regulations and reverse 0:09:55.320 --> 0:09:58.439 osmoses go, which is to say, without without getting into 0:09:58.480 --> 0:10:01.720 all the chemistry, there are certain differences in water flavor 0:10:01.800 --> 0:10:04.880 due to different minerals and other elements in the water. Now, 0:10:04.920 --> 0:10:09.960 another interesting thing about about tap water, especially generally when 0:10:10.000 --> 0:10:17.959 you're drinking tap water, the drinking water probably contains calcium, magnesium, sodium, 0:10:18.040 --> 0:10:22.600 and according to Azolae at All in an article in 0:10:22.640 --> 0:10:26.319 the Journal of General Internal Medicine from two thousand and 0:10:26.360 --> 0:10:28.880 one titled Comparison of Mineral Content of tap water and 0:10:28.920 --> 0:10:33.440 bottled waters, the mineral content of drinking water like this 0:10:33.679 --> 0:10:38.800 ultimately may be an important source of daily recommended mineral dosages, 0:10:39.400 --> 0:10:41.760 certainly in the United States, which was the area they 0:10:41.760 --> 0:10:46.400 were looking at here. And so basically, while we might 0:10:46.480 --> 0:10:48.840 think of water as being this thing that we would 0:10:48.640 --> 0:10:51.360 will just purify the heck out of it, just give 0:10:51.400 --> 0:10:55.280 me the purest water possible, the purest water possible isn't 0:10:55.320 --> 0:10:58.800 necessarily going to be the healthiest or the tastiest, which 0:10:58.880 --> 0:11:01.839 I thought was an interest distinction, like when when we 0:11:02.000 --> 0:11:05.400 when we purchase bottled water, we're not going and buying 0:11:05.440 --> 0:11:08.199 the distilled water usually. I mean, maybe, you know, maybe 0:11:08.240 --> 0:11:09.960 that's what you are doing, but for the most part, 0:11:10.240 --> 0:11:14.720 people are are not buying distilled water for drinking purposes. Right. 0:11:14.880 --> 0:11:17.760 But distilled water, even though it is probably the purest 0:11:17.840 --> 0:11:21.120 form of water you can get, is not necessarily better 0:11:21.320 --> 0:11:24.520 for any reason, not for not for health or for 0:11:24.640 --> 0:11:28.160 experience of drinking. Right now, in terms of just trying 0:11:28.160 --> 0:11:29.880 to get down to the question though, well, what what 0:11:29.960 --> 0:11:32.240 does it taste like? Okay, you know, we're saying it 0:11:32.280 --> 0:11:34.200 can can go a little in this direction, a little 0:11:34.240 --> 0:11:37.200 in that direction. We have these mineral components, uh, you know, 0:11:37.240 --> 0:11:40.040 adding to the to the flavor. But but what is 0:11:40.040 --> 0:11:42.280 the taste itself? And I think one of the interesting 0:11:42.280 --> 0:11:44.240 things about that question is that it forces you to 0:11:44.240 --> 0:11:47.800 take a step back and think about taste itself. Um, 0:11:47.840 --> 0:11:51.880 you know, taste involves both sensations on the tongue and 0:11:52.160 --> 0:11:55.320 olfactory information as well. So it's not only it's not 0:11:55.360 --> 0:11:59.199 only tasting with the mouth, it's smelling, uh whatever you 0:11:59.240 --> 0:12:03.520 know it is that you or consuming as well. And 0:12:04.000 --> 0:12:07.959 certainly we do taste contents in the water, though under 0:12:08.120 --> 0:12:11.080 ideal circumstances that that's not going to push you hard 0:12:11.120 --> 0:12:14.280 in any direction. But obviously, if you dilute some sugar 0:12:14.400 --> 0:12:17.000 in a glass of the universal solvent and drink it, 0:12:17.240 --> 0:12:20.960 you'll find it sweet. Saltwater taste salty. Your sense of 0:12:21.000 --> 0:12:24.160 taste is still weighing in on the water. But in 0:12:24.240 --> 0:12:26.880 terms of this kind of brings us back to the 0:12:26.880 --> 0:12:29.320 same question, does the water itself have a taste or 0:12:29.360 --> 0:12:31.640 is it just the vehicle for these various flavors, be 0:12:31.720 --> 0:12:37.240 it salt or sugar, or a slight hint of magnesium, 0:12:37.280 --> 0:12:41.160 that sort of thing. So one idea proposed in the 0:12:41.200 --> 0:12:45.600 sixties and seventies by psychologist Linda Bartschuk was that the 0:12:45.640 --> 0:12:48.760 taste of water is more of an after taste of 0:12:48.840 --> 0:12:51.959 prior eating and drinking. And this, too, I guess, is 0:12:52.000 --> 0:12:53.720 more in line with the idea of water as the 0:12:53.800 --> 0:12:55.840 vehicle of flavor, but something that is in and of 0:12:55.840 --> 0:13:00.760 itself flavorless. So the idea would be that, like when 0:13:00.840 --> 0:13:04.640 you take a drink of water, you are somehow re 0:13:04.880 --> 0:13:10.280 experiencing flavors of foods you may have eaten most recently. Yeah, 0:13:10.280 --> 0:13:12.480 and this this will become important. And again we have 0:13:12.559 --> 0:13:15.040 to realize that when you take a sip of water, 0:13:15.679 --> 0:13:20.160 you are not introducing water. No matter how sterile your 0:13:20.160 --> 0:13:24.199 water is, your mouth is not sterile. You know your 0:13:24.280 --> 0:13:26.240 your mouth is going to even if you if you've 0:13:26.280 --> 0:13:28.920 just brushed your teeth, great, but that you're going to 0:13:29.000 --> 0:13:34.040 have some semblance of the of that experience in your mouth. 0:13:34.080 --> 0:13:35.880 If you're eating dinner, you know there's going to be 0:13:35.920 --> 0:13:39.360 the hint of food or drink as well. So, yeah, 0:13:39.360 --> 0:13:41.920 you're not introducing the water into a neutral place. If 0:13:41.920 --> 0:13:45.640 nothing else you your saliva is present. Emily Underwood wrote 0:13:45.640 --> 0:13:48.600 in an excellent short twenty seventeen piece for the American 0:13:48.640 --> 0:13:51.480 Association for the Advancement of Science on this topic, the 0:13:51.600 --> 0:13:55.960 Flavor of Water, And at one point she's a sighting 0:13:56.040 --> 0:13:59.040 Zachary Knight, Oh, who is one of the three authors 0:13:59.080 --> 0:14:03.200 of the research summary thirst in Current Biology that I 0:14:03.240 --> 0:14:05.040 was referring to in the last episode and I'll be 0:14:05.280 --> 0:14:08.680 talking about again in a few minutes. Yeah, So Underwood 0:14:08.679 --> 0:14:12.560 points to something that that we discussed in the last 0:14:12.559 --> 0:14:14.840 episode that you know, ultimately, when we're getting into taste, 0:14:15.160 --> 0:14:19.160 when we're getting into water detection in the mouth, the 0:14:19.200 --> 0:14:23.080 molecular and cellular mechanisms here are not that well understood. 0:14:23.520 --> 0:14:28.080 And then she also touches on some of nights research 0:14:28.160 --> 0:14:32.560 regarding the thirst trigger. Uh, you know where where that 0:14:32.720 --> 0:14:35.920 is seems to locate in the brain and then ultimately 0:14:35.960 --> 0:14:38.080 what's where is the trigger in the in the rest 0:14:38.080 --> 0:14:40.080 of the body. But we'll come back to that in 0:14:40.080 --> 0:14:43.240 a bit. Yeah, but I guess there are somewhat separate 0:14:43.320 --> 0:14:48.400 questions for can you detect water in your mouth versus 0:14:48.480 --> 0:14:54.080 can you taste water? I mean those are slightly slightly different, right, yeah, well, 0:14:54.200 --> 0:14:56.880 but but then again when you start thinking about like 0:14:56.920 --> 0:15:00.520 what taste is, maybe they're not that different, like it's 0:15:00.960 --> 0:15:02.840 but but it basically comes down to, yeah, it's not 0:15:02.880 --> 0:15:05.800 about interpreting these minerals or sweetness or saltiness, but like 0:15:06.520 --> 0:15:10.040 the just the basic signal of it is water. It 0:15:10.160 --> 0:15:13.680 is in my mouth, you know, and then ultimately being 0:15:13.720 --> 0:15:17.520 able to tell if something is not water, like or 0:15:17.560 --> 0:15:19.200 if it or if the water is you know, too 0:15:19.200 --> 0:15:21.560 far in a particular direction, like oh it is it 0:15:21.680 --> 0:15:25.600 is actually oil and water and not just water. I 0:15:25.640 --> 0:15:29.160 wanted water. That's sort of question. So research has been 0:15:29.160 --> 0:15:32.760 trying to isolate water sensing taste receptor. It sells on 0:15:32.880 --> 0:15:36.240 the tongue of a particular note. Here is the paper 0:15:36.280 --> 0:15:39.400 The Cellular Mechanism for Water Detection in the Mammalian Taste 0:15:39.440 --> 0:15:43.600 system by Zocchi at All, published in Nature Neuroscience in 0:15:43.640 --> 0:15:48.280 twenty seventeen. This was a team i believe from the 0:15:48.320 --> 0:15:51.760 California Institute of Technology in Pasadena, and they were working 0:15:51.760 --> 0:15:54.280 with mice and this is this is one of those 0:15:54.400 --> 0:15:57.120 the studies that I mean, it's already an interesting area, 0:15:57.240 --> 0:15:59.840 like using mice to figure out how we're tasting, but 0:16:00.000 --> 0:16:04.840 and it goes in ultimately strange directions that are pretty fascinating. 0:16:05.200 --> 0:16:08.280 So they were they were using different varieties of mice 0:16:08.400 --> 0:16:12.760 with specific types of taste receptor cells genetically knocked out 0:16:13.160 --> 0:16:16.680 in order to try and isolate which ones were seemingly 0:16:16.800 --> 0:16:20.240 useful in tasting water. And they found that the acid 0:16:20.360 --> 0:16:24.680 sensing sour taste receptor cells seem to be the most involved. 0:16:25.480 --> 0:16:29.960 Mice with those knocked out took far longer distinguishing oily 0:16:30.000 --> 0:16:34.560 water from clean water. In the words of the study, 0:16:34.920 --> 0:16:39.760 this quote compromise discrimination between water and non aqueous fluids. 0:16:40.360 --> 0:16:43.200 So these cells seem like they may they may well 0:16:43.240 --> 0:16:47.920 be very much involved in the process. Interesting, Okay, so 0:16:48.040 --> 0:16:52.280 if we are actually tasting water, it may rely more 0:16:52.400 --> 0:16:56.520 on the cells that normally taste sourness or acidity than 0:16:56.600 --> 0:16:59.280 other taste receptor cells, or at least in mice, And 0:16:59.360 --> 0:17:01.560 if the same held true in humans, that would be 0:17:01.640 --> 0:17:04.399 the case for us. Right. But this is where the 0:17:04.440 --> 0:17:09.400 mouse experiment from this team gets weird. So to further 0:17:09.480 --> 0:17:12.600 test this out, they bred mice that could taste light 0:17:13.000 --> 0:17:18.120 with these acid sensing TRCs taste receptor cells. They train 0:17:18.240 --> 0:17:20.960 them to drink water from a spigot, and they replace 0:17:21.080 --> 0:17:26.760 that spigot with an optic fiber cable. So they apparently 0:17:26.800 --> 0:17:29.840 treated the mice in this case, they apparently treated the 0:17:29.920 --> 0:17:33.240 light as if they were tasting water, but they didn't stop. 0:17:33.280 --> 0:17:37.840 They kept drinking the light long after they would have 0:17:38.320 --> 0:17:42.680 normally stopped drinking water. So the acid sensing TRCs might 0:17:42.720 --> 0:17:45.919 be involved in triggering drinking, but they might not be 0:17:45.960 --> 0:17:48.640 involved in stopping you from drinking, like saying, Okay, well, 0:17:48.640 --> 0:17:50.800 that's that's all the water I need to drink right now, 0:17:52.440 --> 0:17:55.480 and I'm not sure there may be other complications there. 0:17:55.520 --> 0:17:58.159 I mean, once you have an animal drinking light and 0:17:58.280 --> 0:18:01.159 not actual water. It just seems to me like there 0:18:01.240 --> 0:18:02.879 might there might be other things going on there. I'll 0:18:02.920 --> 0:18:05.639 on a very physical basis, so this would be taste 0:18:05.680 --> 0:18:09.880 receptor cells in the mouth, but they're like optically sensitive cells. 0:18:10.200 --> 0:18:13.480 Am I right about this? It's literally like drinking light 0:18:13.600 --> 0:18:17.720 with their mouth, like letting light shine into the oral cavity. Yes, 0:18:17.960 --> 0:18:21.400 it h I mean, it sounds insane when you say 0:18:21.440 --> 0:18:23.600 it out loud, but but yeah, there's there's actually a 0:18:24.359 --> 0:18:27.840 YouTube video about it from Science Magazine titled these mice 0:18:27.880 --> 0:18:31.840 are drinking light. So if anyone needs to actually see 0:18:31.880 --> 0:18:34.600 what we're talking about here, pull that up. And yeah, 0:18:34.680 --> 0:18:38.239 just it's it's a this, this black mouse going up 0:18:38.280 --> 0:18:41.919 to this um this little receptacle, and it appears to 0:18:41.920 --> 0:18:45.520 be drinking, but there's blue light flooding out of the hole, okay, 0:18:45.520 --> 0:18:48.240 and it's got light sensitive cells in its mouth, So 0:18:48.280 --> 0:18:51.400 the mouse's brain is reacting as if by shining light 0:18:51.480 --> 0:18:56.080 into its mouth it was swallowing water. Yes, that's crazy, man, 0:18:56.720 --> 0:19:00.760 Yeah it is. This is this is it's it's mind 0:19:00.760 --> 0:19:04.640 blowing on several levels here. So ultimately this this all 0:19:04.720 --> 0:19:08.000 might be related to changes in pH level when in 0:19:08.040 --> 0:19:10.560 a normal situation, when you know, a mouse or any 0:19:10.680 --> 0:19:14.400 mammal supposedly is drinking something that is not light. When 0:19:14.440 --> 0:19:18.080 it tries out the water, saliva is washing around in 0:19:18.119 --> 0:19:21.720 the mouth, and the removal of saliva might be key 0:19:21.880 --> 0:19:24.280 to sensing water. Again, coming back to what we said 0:19:24.280 --> 0:19:27.600 earlier about you know, water is not entering into a 0:19:27.640 --> 0:19:30.280 neutral environment when it goes in your mouth. It's going 0:19:30.280 --> 0:19:33.040 to interact with at least saliva, and in doing so 0:19:33.359 --> 0:19:36.280 that might change the pH level which triggers these these 0:19:36.359 --> 0:19:39.840 TRCs on the tongue. That seems to be the basic 0:19:39.880 --> 0:19:43.240 framework we're potentially looking at here. Oh, that's interesting. So 0:19:43.320 --> 0:19:46.600 at least according to the idea here, part of the 0:19:46.720 --> 0:19:51.440 sensation of drinking water might be the water stability to 0:19:51.480 --> 0:19:55.600 wash natural saliva out of the mouth. Right though, of 0:19:55.600 --> 0:20:00.679 course standard caveat that. More researches quired and then we 0:20:00.680 --> 0:20:02.720 still don't We still don't have this one knocked one, 0:20:03.400 --> 0:20:06.520 but it's yeah, it's it. Ultimately, it makes you rethink 0:20:06.560 --> 0:20:10.239 again what taste actually is and consider that there may 0:20:10.240 --> 0:20:12.920 be precise triggers in place for detecting water and distinguish 0:20:12.960 --> 0:20:16.080 it from other liquids. And then also letting you know 0:20:16.119 --> 0:20:18.080 that you have had enough water. Like all these things 0:20:18.119 --> 0:20:19.800 that we just take for granted, we think of them 0:20:19.840 --> 0:20:22.440 as we think of them as choices that we make, 0:20:22.880 --> 0:20:25.680 like I have I am, I've decided now I must 0:20:25.760 --> 0:20:29.159 have water. I have decided now that I don't need 0:20:29.240 --> 0:20:31.640 any more water. But but these are all tied into 0:20:31.840 --> 0:20:42.360 the you know, this intricate biological system. Than all right, well, rob, 0:20:42.440 --> 0:20:45.600 if you're ready, I wanted to discuss some more of 0:20:45.760 --> 0:20:48.920 the things I was reading in that twenty sixteen article 0:20:48.960 --> 0:20:53.320 in Current Biology that was about the biology of thirst. Again. 0:20:53.400 --> 0:20:58.000 This was by David Leeb, Christopher Zimmerman, and Zachary Knight. 0:20:58.560 --> 0:21:00.840 Let's do it all right now. We already talked about 0:21:00.880 --> 0:21:05.000 some of the conditions that will trigger thirst and water 0:21:05.080 --> 0:21:10.040 seeking behavior in animals such as rodents. In humans, commonly, 0:21:10.600 --> 0:21:14.440 one thing would be a decrease in water volume in 0:21:14.520 --> 0:21:16.800 the body. But another thing would be an increase in 0:21:16.920 --> 0:21:22.440 what's called blood osmolality osmol A L I T Y 0:21:23.200 --> 0:21:25.199 I spell it because that word will keep coming up 0:21:25.280 --> 0:21:30.879 in this discussion. Osmolality is the concentration of substances dissolved 0:21:31.160 --> 0:21:34.160 in the water content of the body. So the blood 0:21:34.200 --> 0:21:37.720 osmolality will go up, say if you consume salt or 0:21:37.920 --> 0:21:41.440 consume other kinds of salts of various minerals, whether that's 0:21:41.480 --> 0:21:45.200 sodium or magnesium or whatever, there are lots of things 0:21:45.320 --> 0:21:48.080 dissolved in the blood, and as the concentration of those 0:21:48.200 --> 0:21:51.359 things dissolved in the blood goes up, that's known as 0:21:51.480 --> 0:21:55.600 increasing osmolality. And as we discussed in the last episode, 0:21:55.680 --> 0:21:59.840 you your osmolality really needs to be pretty tightly constrained 0:22:00.080 --> 0:22:03.000 within an ideal range, or it can start leading to 0:22:03.880 --> 0:22:08.240 system wide problems with cellular function because cells need a 0:22:08.400 --> 0:22:12.440 pretty tightly controlled electrochemical gradient on each side of their 0:22:13.040 --> 0:22:17.040 membranes in order to control the passage of ions in 0:22:17.160 --> 0:22:19.200 and out of the cell to you know, take in things, 0:22:19.280 --> 0:22:22.040 the cell needs to release waste products and so forth. 0:22:22.600 --> 0:22:26.080 So in order for your body to work right, it 0:22:26.240 --> 0:22:29.320 needs to have the right level of the right concentration 0:22:29.720 --> 0:22:33.200 of things like salts dissolved in its water. But you 0:22:33.359 --> 0:22:38.360 also have to keep your body, your body's water volume 0:22:38.440 --> 0:22:42.200 at the right level in order to maintain ideal blood 0:22:42.240 --> 0:22:44.960 pressure because that blood's got to flow, and if you 0:22:45.040 --> 0:22:48.320 suddenly are to remove a lot of liquid from the body, 0:22:48.720 --> 0:22:51.399